Synthesis of carbon nanotubes by spray-pyrolysis

The injection CVD or “spray pyrolysis” method is based on the simultaneous injection of a metallocene–hydrocarbon solution through a sprayer into the reaction furnace. The major advantage of the spray-pyrolysis method consists in the direct and continuous generation of fresh catalytic particles throughout the entire growth cycle. This gives the possibility to scale up the method for continuous or semicontinuous production of carbon nanotubes at commercially viable prices. In cooperation with the group lead by Prof Darabont from Babes-Bolyai University, Cluj-Napoca, Romania (, we investigated the quality and quantity of the nanotubes grown by spray-pyrolysis when different experimental parameters, catalysts and carbon feedstock were used.

Well oriented carbon nanotubes


The experimental setup used in our experiments to synthesize carbon nanotubes consist of an electric furnace with an effective heating length of 200 mm, a quartz reactor of 18 mm inner diameter and a nozzle with two concentric tubes of 0.8 and 1.8 mm inner diameter, respectively. The inner tube of the nozzle carries the metallocene–hydrocarbon solution, while the outer one guides the carrier gas in order to pulverize the solution.
Experimental setup

We investigated the effect of the experimental parameters (temperature, catalyst concentration, flow rate of carbon source and carrier gas), the influence of metallocenes (ferrocene, cobaltocene and nickelocene) and hydrocarbons (benzene, toluene, xylene, cyclohexane, cyclohexanone, n-hexane, n-heptane, n-octane and n-pentane) on the quality and quantity of the nanotubes grown by spray-pyrolysis. The product deposited on the walls of the quartz tube was collected and analyzed by transmission and scanning electron microscopy (TEM and SEM), X-ray diffraction, and scanning tunneling microscopy (STM).


MWCNTs were produced with maximum yield when ferrocene–nickelocene catalyst mixture was used and xylene was found to be the most efficient carbon source. For xylene the weight of purified carbon nanotubes normalized to the weight of catalyst material is higher than 50%. Good quality thin MWCNTs were produced from n-octane, but in lower quantity than in case of xylene. Nevertheless, the production of MWCNTs was possible in case of all mentioned hydrocarbons and metallocenes. For xylene the best results were obtained at 800 ºC, 1.5 g ferrocene in 50 ml xylene catalyst concentration, 500 l/h carrier gas flow rate and 1 ml/min carbon source flow rate.

SEM image of the carbon nanotubes
SEM image of the carbon nanotubes

TEM xylene
TEM octane
TEM images of the samples produced of xylene and octane, respectively

Diameter distribution with xylene
Diameter distribution
Diameter distribution of the nanotubes produced of xylene
Comparison of the outer and inner diameters of the carbon nanotubes produced of different carbon sources. The diagram shows the diameter intervals containing 80% of the nanotube diameters measured in the sample.


Tapasztó L., Kertész K., Vértesy Z., Horváth Z. E., Koós A. A., Osváth Z., Sárközi Zs., Darabont Al.,. Biró L. P:
Diameter and morphology dependence on experimental conditions of carbon nanotube arrays grown by spray pyrolysis
Carbon 43 (2005) 970–977.

Last updated: Nov 17, 2005 by Géza I. Márk ,
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